Ulmaridae Family of Jellyfish
One Jellyfish of the UImaridae Family can be found in this website:
Pacific Moon Jellyfish, Aurelia labiata. A representative of the Ulmaridae Family of Jellyfish.
Phylogeny: Ulmarid Jellyfish of the Ulmaridae Family, like coral polyps and sea anemones are in the phylum Cnidaria. This phylum is generally characterized by animals having radial symmetry. Their bodies consist of an inner layer (endoderm) and an outer layer (ectoderm) with the layers separated by a jelly-like mesoglea. All Cnidarians have nematocysts (stinging cells) that they use to capture food. Ulmarid Jellyfish are in the subphylum Medusazoa and the class Scyphozoa. Scyphozoans spend most of their life cycle in the medusa (bell or umbrella shaped) form. As Scyphozoans, these jellyfish lack a vellum, a shelf-like structure around the inside margin of the bell. Ulmarid Jellyfish are in the subclass Discomedusae and the order Semaeostomeae. The Ulmaridae Family is one of five families in this order. The Ulmaridae Family contains nine subfamilies, fourteen genera, and around forty-four species. The etymology of the name Ulmaridae is uncertain.
Morphology: In their polyp form, Ulmarid Jellyfish are cylindrical and attach to a hard surface by a basal disk, similar to a sea anemone. The mouth is surrounded my 16-32 oral tentacles. In this form, they only reach 1-5 mm in height. In their medusa stage, Ulmarid Jellyfish have the classic jellyfish appearance, with long frilly oral arms extending below the center of the bell, and shorter tentacles extending from the margins of the bell. The margins are scalloped with numerous lappets. Four primary radial canals extend from the central stomach to the bell margin. These radial canals connect to a ring canal, and are often branching or anastomosing. Between the lappets are sensory organs that include statocysts for balance and, in some species, ocelli for light detection. Four oral arms extend from the manubrium (central tube under ball), each with folds or frills to increase surface area. Most species have four gonads, which are sometimes visible through the bell. The bell itself may be firm and disk-like or flabby and bag-like. The bells may be transparent, translucent, or opaque. Species within this family are not easily distinguished without looking closely at their anatomy. Keys include simple or branched radial canals and a ring-canal; with or without subgenital pits. Some species of Ulmarid Jellyfish have a bell with a maximum diameter of 40 cm (16 inches), and some have oral arms that can reach 7.0 m (23 feet) in length.
Habitat and Distribution: In their polyp stage, Ulmarid Jellyfish are benthic. In their medusa stage they are generally found in open water. They propel themselves through the water by opening and closing their bell. Their swimming ability is limited, and they are largely at the mercy of ocean currents. While they are generally a pelagic species, currents can push them into bays and estuaries. Some species in this family are found near the surface, but others are found at depths of at least 1,500 m (4,920 feet). Ulmarid Jellyfish are found worldwide, in tropical to polar waters. At least four species from this family are found in Mexican waters.
Reproduction: In the medusa stage, Ulmarid Jellyfish are gonochoric (either male or female) and reproduce sexually. The male releases sperm into the water. The female uses her oral arms and tentacles to gather the sperm to fertilize her eggs. The female carries the fertilized eggs on her oral arms. The eggs develop in to planula larvae. The larvae are free swimming until they find suitable habitat and settle to the bottom as polyps. At this stage they undergo asexual reproduction through strobillation. Strobillation is a process whereby miniature medusae (strobilla) are formed into a pancake-like stack on a stalk. The most mature strobilla are at the top of the stack. The strobilla then bud off as individual baby jellyfish (eyphyra). Some species in this family bypass the polyp stage and retain the embyos in a specialized brood chamber until they are released as miniature medusas. This is known as viviparity.
Ecosystem Roles: Ulmarid Jellyfish feed by trailing their tentacles and oral arms through the water and paralyze their prey with their nematocysts. The oral arms then move the prey to the mouth. They feed primarily on small crustaceans, ctenophores, mollusks, tunicates, and other jellyfish. Ulmarid Jellyfish are preyed upon by parasitic crustaceans, fish, sea birds, sea turtles and other jellyfish. Ulmarid Jellyfish sometimes play host to commensal amphipods and fish.